I would get a tandem axle. Get one with brakes #1 for safety reasons, and #2 because it will wear the breaks on your truck fast if you tow heavy loads. I tow a tandem axle 16ft with a Nissan Titan and it eats brakes. Gross weight for my 16ft is about 5100lbs. 3000lb load and trailer weight of roughly 2100lbs.

I only have experience with tandems but some on here who have used both say tandems tow better than single axles.

That is a heavy trailer. I have a heavy duty 16 x 8.5 Tandem with 3500 lb axel and surge brakes weighs 1600 lbs.